In recent years, along with the development of the key technologies for liquid crystal display (LCD) and digital light processing (DLP), an electronic projection display system with a large-size screen and high brightness has been widely used for displaying multimedia information. Projectors, LCD panels and plasma display panels (PDPs) have attracted more and more attentions in the market. For a display device with a size smaller than 30 inches, the LCD panel has become a mainstream product in the market; for a display device with a size within a range from 30 inches to 70 inches, the PDP has become a mainstream product; and for a display device with a size greater than 70 inches, the projector has become a mainstream product.
However, when an image is projected by the projector onto a scattering surface, a projected light beam may be adversely affected by an ambient light beam, and a gamut and a contrast of the image may be degraded when the projected light beam is mixed with the ambient light beam and then scattered. As a result, a display effect will be adversely affected.